/*
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

/*
 *
 *
 *
 *
 *
 * Written by Doug Lea and Josh Bloch with assistance from members of JCP
 * JSR-166 Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util;

/**
 * 一个SortedMap扩展了navigation方法，为给定的搜索目标返回最接近的匹配。
 * 方法lowerEntry, floorEntry, ceilingEntry, 和 higherEntry返回
 * Map.Entry对象，分别与小于、小于或等于、大于或等于、大于给定键关联的条目对象，如果没有这样的键，则返回null。
 * 类似地，方法lowerKey、floorKey、ceilingKey和higherKey只返回关联的键。所有这些方法都是为定位而设计的，而不是遍历条目。
 *
 * <p>可按升序或降序键顺序访问和遍历NavigableMap。
 * descendingMap方法返回映射的一个视图，该视图具有所有反向的关系和反转方向的方法。
 * ascending操作和视图的性能可能比descending操作和视图的性能更快。
 * 方法subMap、headMap和tailMap与类似名称的SortedMap方法不同，它们接受额外的参数来描述下界和上界是包含的还是排他的。
 * 任何NavigableMap的子映射都必须实现NavigableMap接口。
 *
 * <p>该接口还定义了firstEntry、pollFirstEntry、lastEntry和pollLastEntry方法，
 * 这些方法返回和/或删除最小和最大的映射(如果存在的话)，否则返回null。
 *
 * <p>返回entry方法的实现应该返回Map.Entry对，表示生成映射时的快照，因此通常不支持可选的setValue方法。
 * 但是请注意，可以使用put方法更改关联映射中的映射。
 *
 * <p>方法subMap(K, K)、headMap(K)和tailMap(K)被指定为返回SortedMap，
 * 以允许对SortedMap的现有实现进行兼容的改进以实现NavigableMap，但是这个接口的扩展和实现被鼓励重写这些方法以返回NavigableMap。
 * 类似地，可以覆盖keySet()来返回NavigableSet。
 *
 *
 * @author Doug Lea
 * @author Josh Bloch
 * @param <K> the type of keys maintained by this map
 * @param <V> the type of mapped values
 * @since 1.6
 */
public interface NavigableMap<K,V> extends SortedMap<K,V> {
    /**
     * 返回严格小于给定键的与最大键关联的键-值映射，如果没有这样的键，则返回null。
     *
     * @param key the key
     * @return an entry with the greatest key less than {@code key},
     *         or {@code null} if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    Map.Entry<K,V> lowerEntry(K key);

    /**
     * 返回严格小于给定键的最大键，如果没有这样的键，则返回null。
     *
     * @param key the key
     * @return the greatest key less than {@code key},
     *         or {@code null} if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    K lowerKey(K key);

    /**
     * 返回与小于或等于给定键的最大键相关联的键-值映射，如果没有这样的键，则返回null。
     *
     * @param key the key
     * @return an entry with the greatest key less than or equal to
     *         {@code key}, or {@code null} if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    Map.Entry<K,V> floorEntry(K key);

    /**
     * Returns the greatest key less than or equal to the given key,
     * or {@code null} if there is no such key.
     *
     * @param key the key
     * @return the greatest key less than or equal to {@code key},
     *         or {@code null} if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    K floorKey(K key);

    /**
     * 返回与大于或等于给定键的最小键关联的键-值映射，如果没有这样的键，则返回null。
     *
     * @param key the key
     * @return an entry with the least key greater than or equal to
     *         {@code key}, or {@code null} if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    Map.Entry<K,V> ceilingEntry(K key);

    /**
     * 返回大于或等于给定键的最小键，如果没有这样的键，则返回null。
     *
     * @param key the key
     * @return the least key greater than or equal to {@code key},
     *         or {@code null} if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    K ceilingKey(K key);

    /**
     * 返回与严格大于给定键的最小键关联的键-值映射，如果没有这样的键，则返回null。
     *
     * @param key the key
     * @return an entry with the least key greater than {@code key},
     *         or {@code null} if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    Map.Entry<K,V> higherEntry(K key);

    /**
     * 返回严格大于给定键的最小键，如果没有这样的键，则返回null。
     *
     * @param key the key
     * @return the least key greater than {@code key},
     *         or {@code null} if there is no such key
     * @throws ClassCastException if the specified key cannot be compared
     *         with the keys currently in the map
     * @throws NullPointerException if the specified key is null
     *         and this map does not permit null keys
     */
    K higherKey(K key);

    /**
     * 返回与此映射中最小键关联的键-值映射，如果映射为空则返回null。
     *
     * @return an entry with the least key,
     *         or {@code null} if this map is empty
     */
    Map.Entry<K,V> firstEntry();

    /**
     * 返回与此映射中最大键关联的键-值映射，如果映射为空则返回null。
     *
     * @return an entry with the greatest key,
     *         or {@code null} if this map is empty
     */
    Map.Entry<K,V> lastEntry();

    /**
     * 删除并返回与此映射中最小键关联的键-值映射，如果映射为空则返回null。
     *
     * @return the removed first entry of this map,
     *         or {@code null} if this map is empty
     */
    Map.Entry<K,V> pollFirstEntry();

    /**
     * 删除并返回与此映射中最大键关联的键-值映射，如果映射为空则返回null。
     *
     * @return the removed last entry of this map,
     *         or {@code null} if this map is empty
     */
    Map.Entry<K,V> pollLastEntry();

    /**
     * 返回此映射中包含的映射的逆序视图。descending映射由该映射支持，因此对映射的更改反映在descending映射中，反之亦然。
     * 如果在对任何一个map的集合视图进行迭代时(除了通过迭代器自己的删除操作之外)，其中一个map被修改，那么迭代的结果是未定义的。
     *
     * <p>返回的映射的顺序相当于Collections.reverseOrder(comparator())。
     * 表达式{@code m.descendingMap().descendingMap()}返回一个m的视图，它本质上等价于m。
     *
     * @return a reverse order view of this map
     */
    NavigableMap<K,V> descendingMap();

    /**
     * 返回包含在此映射中的键的NavigableSet视图。
     * 集合的迭代器按升序返回键。集合由映射支持，因此对映射的更改将反映在集合中，反之亦然。
     * 如果在对集合进行迭代时修改了映射(除了通过迭代器自己的删除操作)，则迭代的结果是未定义的。
     * 集合支持元素删除，它通过Iterator.remove, Set.remove, removeAll, retainAll, and clear 操作。
     * 它不支持add或addAll操作。
     *
     * @return a navigable set view of the keys in this map
     */
    NavigableSet<K> navigableKeySet();

    /**
     * 返回包含在此映射中的键的逆序NavigableSet视图。
     * 集合的迭代器按降序返回键。集合由映射支持，因此对映射的更改将反映在集合中，反之亦然。
     * 如果在对集合进行迭代时修改了映射(除了通过迭代器自己的删除操作)，则迭代的结果是未定义的。
     * 集合支持元素删除，它通过Iterator.remove, Set.remove, removeAll, retainAll, and clear 操作。
     * 它不支持add或addAll操作。
     *
     * @return a reverse order navigable set view of the keys in this map
     */
    NavigableSet<K> descendingKeySet();

    /**
     * 返回该映射中键值范围从fromKey到toKey的部分的视图。
     * 如果fromKey和toKey相等，则返回的映射为空，除非fromInclusive和toInclusive都为true。
     * 返回的映射得到此映射的支持，因此返回映射中的更改将反映在此映射中，反之亦然。
     * 返回的映射支持此映射支持的所有可选映射操作。
     *
     * <p>返回的映射将抛出一个IllegalArgumentException，
     * 用于试图将一个键插入到它的范围之外，或者构造一个其端点位于它的范围之外的子映射。
     *
     * @param fromKey low endpoint of the keys in the returned map
     * @param fromInclusive {@code true} if the low endpoint
     *        is to be included in the returned view
     * @param toKey high endpoint of the keys in the returned map
     * @param toInclusive {@code true} if the high endpoint
     *        is to be included in the returned view
     * @return a view of the portion of this map whose keys range from
     *         {@code fromKey} to {@code toKey}
     * @throws ClassCastException if {@code fromKey} and {@code toKey}
     *         cannot be compared to one another using this map's comparator
     *         (or, if the map has no comparator, using natural ordering).
     *         Implementations may, but are not required to, throw this
     *         exception if {@code fromKey} or {@code toKey}
     *         cannot be compared to keys currently in the map.
     * @throws NullPointerException if {@code fromKey} or {@code toKey}
     *         is null and this map does not permit null keys
     * @throws IllegalArgumentException if {@code fromKey} is greater than
     *         {@code toKey}; or if this map itself has a restricted
     *         range, and {@code fromKey} or {@code toKey} lies
     *         outside the bounds of the range
     */
    NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive,
                             K toKey,   boolean toInclusive);

    /**
     * 返回映射中键值小于(或等于，如果inclusive为true)toKey部分的视图。
     * 返回的映射得到此映射的支持，因此返回映射中的更改将反映在此映射中，反之亦然。
     * 返回的映射支持此映射支持的所有可选映射操作。
     *
     * <p>返回的映射将抛出一个IllegalArgumentException，
     * 用于试图将一个键插入到它的范围之外，或者构造一个其端点位于它的范围之外的子映射。
     *
     * @param toKey high endpoint of the keys in the returned map
     * @param inclusive {@code true} if the high endpoint
     *        is to be included in the returned view
     * @return a view of the portion of this map whose keys are less than
     *         (or equal to, if {@code inclusive} is true) {@code toKey}
     * @throws ClassCastException if {@code toKey} is not compatible
     *         with this map's comparator (or, if the map has no comparator,
     *         if {@code toKey} does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if {@code toKey} cannot be compared to keys
     *         currently in the map.
     * @throws NullPointerException if {@code toKey} is null
     *         and this map does not permit null keys
     * @throws IllegalArgumentException if this map itself has a
     *         restricted range, and {@code toKey} lies outside the
     *         bounds of the range
     */
    NavigableMap<K,V> headMap(K toKey, boolean inclusive);

    /**
     * 返回映射中键值大于(或等于，如果inclusive为true)fromKey的部分的视图。
     * 返回的映射得到此映射的支持，因此返回映射中的更改将反映在此映射中，反之亦然。
     * 返回的映射支持此映射支持的所有可选映射操作。
     *
     * <p>返回的映射将抛出一个IllegalArgumentException，
     * 用于试图将一个键插入到它的范围之外，或者构造一个其端点位于它的范围之外的子映射。
     *
     * @param fromKey low endpoint of the keys in the returned map
     * @param inclusive {@code true} if the low endpoint
     *        is to be included in the returned view
     * @return a view of the portion of this map whose keys are greater than
     *         (or equal to, if {@code inclusive} is true) {@code fromKey}
     * @throws ClassCastException if {@code fromKey} is not compatible
     *         with this map's comparator (or, if the map has no comparator,
     *         if {@code fromKey} does not implement {@link Comparable}).
     *         Implementations may, but are not required to, throw this
     *         exception if {@code fromKey} cannot be compared to keys
     *         currently in the map.
     * @throws NullPointerException if {@code fromKey} is null
     *         and this map does not permit null keys
     * @throws IllegalArgumentException if this map itself has a
     *         restricted range, and {@code fromKey} lies outside the
     *         bounds of the range
     */
    NavigableMap<K,V> tailMap(K fromKey, boolean inclusive);

    /**
     * {@inheritDoc}
     *
     * <p>等于 {@code subMap(fromKey, true, toKey, false)}.
     *
     * @throws ClassCastException       {@inheritDoc}
     * @throws NullPointerException     {@inheritDoc}
     * @throws IllegalArgumentException {@inheritDoc}
     */
    SortedMap<K,V> subMap(K fromKey, K toKey);

    /**
     * {@inheritDoc}
     *
     * <p>等于 {@code headMap(toKey, false)}.
     *
     * @throws ClassCastException       {@inheritDoc}
     * @throws NullPointerException     {@inheritDoc}
     * @throws IllegalArgumentException {@inheritDoc}
     */
    SortedMap<K,V> headMap(K toKey);

    /**
     * {@inheritDoc}
     *
     * <p>等于 {@code tailMap(fromKey, true)}.
     *
     * @throws ClassCastException       {@inheritDoc}
     * @throws NullPointerException     {@inheritDoc}
     * @throws IllegalArgumentException {@inheritDoc}
     */
    SortedMap<K,V> tailMap(K fromKey);
}
